[Objective]This study was conducted to clarify the mechanism of respiratory disorder in the postoperative state in patients with esophageal cancer.[Background data]Translocational endotoxemia has been demonstrated in the postoperative and postburnt state in animals. Endotoxin is known to lead to the clinical manifestation of respiratory disorder. But the occurrence of endotoxemia had not been confirmed in the early postoperative state in patients with esophageal cancer. Then, we hypothesized that H_2O_2 production during the operation leaded to the respiratory disorder.[Methods]We used the computer image-analyzing system and 2', 7'-dichlorofluorescin diacetate for the marker of H_2O_2 production in vivo.[Results]H_2O_2 production in the pulmonary microcirculation of the lt. pulmonary artery blocked rabbits was higher than those of the lt. main bronchus blocked rabbits and control rabbits at each time point. In high-power view, H_2O_2 was detected in granulocytes.[Conclusions]Insuficient pulmonary circulation due to operative procedure may cause the respiratory disorder in the early postoperative state in patients with esophageal cancer.